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Tesla Wall Charger Wire

Discussion in 'Model 3: Battery & Charging' started by zero610, Jun 14, 2018.

  1. zero610

    zero610 Member

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  2. eprosenx

    eprosenx Member

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    #2 eprosenx, Jun 15, 2018
    Last edited: Jun 15, 2018
    Yes, that would work fine. Assuming your breaker has 75c listed terminals (which I think basically everything does nowadays) you can use the 75c rating of the wire which allows 6 gauge copper to be used for 48 amps of continuous load (need a 125% rating which is 60 amps and that wire is rated to 65 amps at 75c).

    However: That wire has three 6 gauge conductors plus a ground wire. You don't need a neutral so you would be wasting one of the wires and have to cap it off or something. Copper is expensive so it sucks to waste it!

    I did my Wall Connector in EMT pipe and fished the wires through (THHN #6 gauge wire). I only had to go about 10 feet so this was a lot cheaper. I did my NEMA 14-50 (in addition to the wall connector) in flex conduit which I also fished the wires through - but that one required a neutral so it was three #6's plus a #10 ground.

    One option for you would be to do flex conduit and fish your own conductors in. I used a #10 ground wire for my 60 amp circuit wall connector - so 48 amps usable (as that was allowed by code). Though this is usually done for somewhat shorter runs. Fishing a full 50 feet might be a pain (and I am not sure if there is a limit to how far you are allowed to use flex conduit since fishing it would be a pain and could damage the conductors - though I don't know of any code section that prohibits this - it looks like any prohibition on this may have been previously removed but I would check with your inspector before making a decision).

    Edit: Now I am thinking about that wire you linked to some more. It has a very small "ground" wire (I think in this case they may technically refer to it as a "bond wire". It is expected to work in concert with the armor to provide a low resistance path to ground. So I am guessing if you used this into the non-metallic wall connector you would need to ensure the armor and the bond wire were both tied together at the wall connector end and onto the ground terminal of the Wall Connector. That way both would help provide the grounding/bonding path together. I am not sure if this would require a bushing with a ground connector on it or what. I did mine with a dedicated #10 ground wire that I landed directly on the wall connector ground terminal. I did put a bushing on the rigid pipe end that I ran into the wall connector from the back but it was not the type with a ground screw on it. I was/am wondering if I should have used a grounding one and tied it together as well. There is not a lot of room in the wall connector if you don't use the backplate extension thing.
     
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  3. eprosenx

    eprosenx Member

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    So you could use something like this that only has two 6 gauge conductors:

    6/2 MC Cable w/ Ground, 250ft or 1000ft

    Though that web site does not call it out for residential use, I have a hard time understanding why it would not be allowed in residential. Typically commercial standards are the more rigorous ones.

    Here is another example of the same stuff:
    6/2 w/Ground, MC, Aluminum Armor, Stranded - 62MCAGSTRX125, Conductor, Armored Cable, Wire, Cables, Cords - Platt Electric Supply

    Interesting that neither place provides a "cut to length" option. Platt at least sells it in 125 foot increments.

    Oh, and this type of cable has a dedicated ground wire that does not require both the outer armor and the bonding wire put together. I believe this has a dedicated ground of the required ampacity.
     
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  4. zero610

    zero610 Member

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    Appreciate the reply. I do like the 6/2 you mentioned; however I need to find it less than 125 ft, which negates any price savings. If I can't find anything less than 125 ft of 6/2 armored wire, it there any harm is using the originally linked 6/3 and using the 3rd neutral wire as the grounding wire? I know the wire color will not be green...
     
  5. zero610

    zero610 Member

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  6. eprosenx

    eprosenx Member

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    Interesting question about using it for ground! I had not considered that.

    So there are allowances in the NEC for changing the "color" of a wire. Around requirements to make sure it is "permanently marked". I think these have changed over different code rev's. A very common thing I see is wrapping the wire in colored electrical tape at the end pigtails as a marking, but I am not sure if that meets current code. Typically where I see wire colors changed is when using a 12/2 wire with a white and black wire for 240v so you are changing the white wire into a hot. Or another case is on service entrance cable where you have three black colored conductors coming out of a conduit and you wrap one in white electrical tape to indicate the neutral.

    From a practical standpoint, the wall connector has a much smaller lug for grounding and it is in a different spot on the PCB. You would want to make sure a 6 AWG would fit under there without damaging the PCB and that you could route the wire OK. Also, you would still need to ground the sheath of the armored cable back at the electrical box (along with the bond wire) so it was not "floating". I am unsure if you would also be require to bond both of those with this "other" ground wire as well at the HPWC end. Typically in any electrical box where connections are made you are required to connect all grounds together and connect them to the electrical box as well. I am not sure if the HPWC counts for this. In my case, I did not do it in the HPWC and I rely on my Rigid + EMT conduit coming into the back of the HPWC to be grounded at the panel end. It passed inspection, but the guy never looked at it. <shrug> Not a lot of room in the HPWC so I kept stuff in there to a minimum.

    I think I have heard of them before. But I don't think I have ever ordered from them. Seems legit to me. Though I would be kind of surprised if you could not find a supply house in Texas willing to cut you a custom length. There are a lot of electric supply houses around the country. Greybar and Platt Electric are big ones around here.
     
  7. zero610

    zero610 Member

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    I'll call around to some local places. Good suggestion.

    One more question for ya - again appreciate the help.

    I have a main panel (200 amp breaker) and sub panel (100 amp breaker). When adding the 60 amp fuse for the tesla home charger, is it best to put it on the main or the sub panel? There are free spaces on both panels; however most all of the large draw items are on the main panel already (A/C systems, Appliances, Dryer, etc).
     
  8. zero610

    zero610 Member

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    Panel Pictures
    Main.jpg Sub.jpg
     
  9. eprosenx

    eprosenx Member

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    Hrm, the stupid forum is malfunctioning for images. I only can see one right now. Can you try posting again or put it on Google Photos or something and do a link to it?

    Typically, I would always want to put high power stuff in the main panel. Just less connections and things to go wrong. And also, you don't have to capacity plan on the feeder to the sub, etc... In general, if a sub panel is required due to a number of slots issue I would put all the "big" loads on the main and do the small ones on the sub.

    Oh, and the proper way to do things is to do a "load calculation" for the entire house, and then also for the sub panel and it's feeder from the main panel for that subset of the load to ensure the feeder and panel is of sufficient ampacity. Let's see what your main panel looks like and go from there.
     
  10. zero610

    zero610 Member

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  11. Rocky_H

    Rocky_H Active Member

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    6/2 should be really common stuff, so almost any place that sells electrical equipment, even Lowe's or Home Depot should be able to sell cut-to-length pieces of it.
     
  12. eprosenx

    eprosenx Member

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    Wow, that is a nice clean install. I presume the reason for the subpanel was because a single panel was not going to be enough, and the electrician was smart enough to not fully load the first panel in case you wanted to add anything to it. Really nice!

    So the photo is not zoomed out enough to see the main breaker. I assume it is 200a?

    I would definitely put the Tesla charger into the main panel then.

    Now the question is what do the load calculations say about your house? It is possible that you will be limited by your 200a main feed. It is possible you would need to set the wall connector to a slower charge speed if you don't have enough headroom (hopefully not).

    Can you also post pictures of your "breaker schedule" (i.e. the list of what everything is?) and also the specific stickers on the panel that outline all the gory details about the panel specs?

    I have never done a full load calculation myself, but I have read quite a bit about it. I winged it on my house since I have zero 240v loads other than the AC unit (heat is gas, stove/oven is gas, dryer is gas, water heater is gas). Yours might be closer to the bone. Part of the calculation involves the square footage of the house, etc... And technically you need to go read the nameplates of all the fixed devices (stove, dishwasher, bathroom fans, etc...) - though I think you can get pretty close with estimates. There are a lot of forms online from various sources you can find.

    Also, do you have any electrical panels on the outside of your house like at the meter base? Just want to make sure there are not any additional circuits there that are not in these two panels.
     
  13. eprosenx

    eprosenx Member

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    Someone brought up this calculator in another thread:

    electrician2.com Wire Size calculator

    Note that it may not be updated with 2017 NEC and who knows if it is accurate, but it seems pretty good.

    I am learning some more about AC (formerly called BX) and MC. It seems to me that MC is superior since it has a full size (well whatever the needed size is) dedicated ground conductor.

    A little BS on BX cables. Armored or Metal Clad Cables used in exterior installations.Wenatchee and Chelan Real Estate Inspection Services. | NCW Home Inspections, LLC

    Now this tool makes me concerned that AC cable may also have 60c derate requirements in some instances since there is an option for it in the terminal temp dropdown. I need to read more... MC cable in this tool does not have that option, so hopefully it is good to use at the 75c conductor rating?

    Also, will this be run in any insulation areas? There are some rules around running in insulation since it does not allow as much heat dissipation.
     
  14. zero610

    zero610 Member

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    Correct, 200 amp main.

    Main panel schedule:

    https://photos.app.goo.gl/WSVaetcc8DgotoEj7

    Sub panel schedule:

    https://photos.app.goo.gl/GTmYKX4pizvM2e4F7

    As far as the panel specs, all I could find was what seemed to be info on the panel cover. I might need to remove the panel cover for more details (tomorrow pictures).

    There is an external fuse at each of the outside A/C units (2X) - each has a single fuse in external box. Another cutoff? Not 100% sure...Nothing at the meter base.

    Additional details:

    Surface garage install - no wet or insulation.
    4600 sq ft house
    30amp dryer unused (have gas)

    The load calculator is a bit over my head....

    Learning as I go. Thanks for the instruction!
     
  15. Stoney35

    Stoney35 Member

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    I ran 6/3 Romex to my HPWC since it was all indoors. I decided on 6/3 over 6/2 so that I could take the HPWC with me if I moved and replace it with a NEMA 14-50. Would just have to put in a 50A breaker instead of the 60A breaker.
     
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  16. eprosenx

    eprosenx Member

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    Hrm, yeah, most panels have a few more details than that (like what types of breakers are allowed, etc...)

    Yeah, those are just disconnects for when technicians work on them. Probably also where they have fuses which I think are there to protect the motor windings. You have to size breakers pretty big on motors to keep them from blowing when the motor starts up (surge current) so they generally have something else in the circuit for over current protection.

    Do you have any other devices other than the gas dryer that are out of service (i.e. gas?). I am in the same boat. All gas oven/range and gas dryer. I am not sure how NEC considers outlets and breakers that are installed but not in use. I personally would not count them against your load calcs, but I could see some hard inspector wanting the receptacle removed and blanked over so it would not be easy to just have a future homeowner plug into them.

    Do you have two ovens? Or one oven and one range separate?

    So some notes on your pictures:
    I would definitely work on a load calculation for your house. You have a pretty big house with some extra stuff in it (dual AC units, dual ovens, etc...) and so you are likely not too far from the cusp of needing to have gone to a 320/400a electrical service. I suspect you have some headroom for car charging, but I would calculate it.
    What is your Authority Having Jurisdiction? A City? A County? - What version of NEC are they currently following (and do they have a web site where they list all the exceptions and changes they make to it) - My county follows the state code and the state code follows 2017 NEC but with modifications.
    I wonder if we can find a pre-canned spreadsheet / calculator tool for the load calcs that apply to the version of the code you are permitted under.
    Technically you need to go pull nameplate values from all the hard wired stuff (AC units, furnaces, jacuzzi, dishwasher, disposal, ovens, etc...) - some spreadsheets/tools I have seen have estimated values

    If I were you, I would consider getting one of these: The Sense Home Energy Monitor I have one and it is fantastic for letting me figure out how much power my house is drawing. While this does not help NEC wise, it could help you gain a lot of comfort in how close to the margins you are or are not power wise on your mains. I would buy a 15a 240v breaker to hook it to and put that in your main panel (it needs like zero power, but it just wants 240v so it can monitor voltage on both phase legs).

    I just looked through the 2017 code for AC vs MC and there is a section about AC being limited to 60c insulation ampacity tables if run in insulation, but I don't think it is derated in any other situations. I did not see any notes about any limits on MC cable, so I am assuming that is good at the 75c rating.

    Where do you want to put your wall connector? Pictures? I used EMT hard pipe conduit for mine. I think it looks a lot cleaner, but it is kind of complicated. Exactly how far are you going? Would "flex" be an option? They sell like 25' 3/4ths inch spools at Home Depot.

    Here is my conduit I bent to my wall connector (outside) - I did a lot more panel work after this picture was taken

    ConduitToWallConnector.jpg
     
  17. eprosenx

    eprosenx Member

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    Smart! So did you wire nut cap off the white wire at the wall connector, and properly land it on the neutral bus on the other end just to keep it from "floating"? That is a good idea for future. I ran 3/4'ths conduit so it would be easy to add another conductor later if the HPWC outside got swapped to something else. I installed a NEMA 14-50 inside just in case I want to charge inside or to test my UMC or have a friend come over to charge...

    Also, as being discussed in other threads right now - Romex (NM cable) 6 gauge is NOT rated to be allowed on a 60a breaker from what I can tell. It is because it is limited to 60c insulation rating which limits ampacity to 55 amps. So if you have it on a 60a breaker I am 90% sure you are not code compliant.

    I did mine in hard pipe with THHN wiring and so that let me use #6 on a 60a breaker.
     
  18. eprosenx

    eprosenx Member

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    Here is my NEMA 14-50 setup. 3/4 in flex conduit going from panel to receptacle. Three #6 gage with a #10 ground. 50 amp breaker. I could have done #8 gauge conductors had I not bought the crummy receptacle box with a receptacle only rated for 60c. Buy the Eaton one if you go to Home Depot. I missed that they stocked both and the Eaton one is vastly superior.

    3/4ths in EMT to the right is going to the outdoor Wall Connector. I have two #6 gauge and one #10 ground in it. 60a breaker.

    1/2 in EMT going up is for generator inlet.

    Then the flex whip that came with the transfer panel connects the main panel to the transfer panel. It is *full* of wire!

    55B403FD-FDF3-47B5-96A5-641B8C0A3856.jpeg
     
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  19. zero610

    zero610 Member

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    Found the website below for a quick whole house load calculation. I know it isn't exact. Showing around 155 amp load with the 48 amp tesla wall charger. Thoughts?

    Whole House Load Calculator

    My calculation:

    Load.pdf
     
    • Informative x 1
  20. P85_DA

    P85_DA Supporting Member

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    @zero610 do you plan on running everything at the same time ? I have similar size house 4200sqft 2acs 2 ovens etc etc ...I charge over night when most of that stuff isn’t on ..I also have 200a house service ..running a 100a circuit to the wall connector ::I set car at ~40a as I don’t need fast charging overnight ..it’s only a handful of times I have used the full 80a for S or full 72a for X ...you will be fine putting a 100a breaker o_O
     

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